mindstalk | (Reply)

What you basically are saying in scenario one is that we would double the solar infall, right? That's probably a bad idea, but I can't say how fast we'd reach a new balance between incoming and outgoing radiation because I think lots of feedback mechanisms, like cloud cover, would kick in.

But let us make some sort of thought experiment. Double incoming solar radiation would mean if a very rough calculation shows a temperature rise of slightly less than 50 degrees for the global average, which I think would put us into the very dangerous zone of runaway greenhouse heating, because of the increased water vapor content. If the Earth's weather/ocean system still work to redistribute the heat as it does now the oceans might not cook directly in the tropics, but the redistribution would also mean that most or even all of the planet would go too hot for human tolerance. I mean, that increase in solar infall would make the poles receive as much solar infall as the tropics do now, but the poles are from an energy budget view also warmed by a lot of heat transfer and the tropics cooled by the same transfer.

Anyway, if we assume the elimination of sunset, so to speak would give us one real noon and one mirror noon, I'd guess that we might get a - non-feedback-adjusted - temperature rise looking a bit wobbly, because late afternoon (and after-mirror-noon) probably would give a little dip in temperatures due to air mixing. But potentially a ten-degree rise in temperature per 24h-day until new balance for a normal midlatitude place is reached. But you'd get major effects in the soil and atmosphere systems too, like how far into the ground the heat would penetrate.

The second question. Note first that the tropics are a much larger area than the poles, so cutting incoming radiation by half there if perhaps not a good option.

Plants have adjusted to different energy budgets. So it depends. They have adjusted to seasonal and daily variations too, so giving them constant light might mess up the growth cycle or cause photoinhibition. If constant sunlight means a drier surface (no dew) that would also limit productivity. You might get a situation where C4 plants are globally more competitive, which would be a major biogeographical event and certainly affect what you are likely to eat. The basic thing to remember, however, is that photosynthesis if both rather ineffective when you look at incoming radiation and that a lot of things other than sunlight limit how effective photosynthesis is. Like water availability.